Attic inlet

ABSTRACT

An attic inlet has a square tube to communicate between an attic and a room through a substrate, and a lid to permit airflow through the inlet when open, and prevent it when closed. The lid is moved by an upper pull bar and lower connecting bars attached to the lid. Upper pull bar and lower connecting bars are attached by clevis pins to yoke arms pivoting about parallel axles. Movement of the upper pull bar rotates the yoke arms, and so lowers the connecting bars and the attached lid. Springs urge pull bar and lid into closed default position, while a cord is used to displace pull bar and lid into open position. The lid is attached by tabs on the connecting bars passing through the lid, and lid locking bars engaging apertures in the tabs.

This invention is directed to an attic inlet for ventilating a livestock barn, typically for hogs or poultry, although it is not restricted to particular livestock.

BACKGROUND AND PRIOR ART

Ventilation is important in livestock barns in general and hog barns in particular. Attic inlets allow air to exchange between the attic space of a barn above a ceiling, usually to provide an intermediate temperature acting as a buffer, between the barn interior and the outside.

Attic inlets are generally rectangular housings with a lid or lids which can be closed preventing air interchange between attic and barn interior or open allowing air interchange. Typically there are a plurality of inlets with lids all controlled from a central point, which open together to the same extent. The inlet housing is typically a short rectangular or square tube set in the barn ceiling, with a lid or lids which can be opened. In one form there is a fixed panel transverse to the tube, and louvers set in opposed sides of the tube, sometimes all four sides. U.S. Pat. No. 6,475,078, to Borcherding, 5 Nov. 2002, teaches such a device, which has counterweighted louvers which are opened by air pressure to provide air exchange, a shutoff louver is also provided. In another form the lid(s) are transverse to the tube axis. A single lid may be hinged or pivoted on one side, in which case it is lowered to open position to allow air exchange. Double lids may be pivoted centrally and lowered to provide air exchange, alternatively they may be pivoted at their outer edges and lowered to provide air exchange. In another form the lid may be lowered horizontally to provide air exchange.

Typically the lid is controlled by a cable, cord, string, wire or the like, which may open the lid or close the lid, the default position is closed. Counterweights or springs can be used to either urge the lid closed or open. Lids may have manual shutoffs as well. In general since the ventilation is effected by fans, the lids default position is shut when the fans are off. Cables, cords, strings, wires and the like stretch in use, so springs or counterweights are preferably used to keep the lid(s) shut when not in use. The cable, cord, string or wire and the like is then used to open the lid(s) against counterweight or spring. It is preferred that the cable, cord, string, wire and the like be machine controlled, and more preferably that one machine control all the air inlet lids in a building, so that they can be actuated together.

A particular one lid four way inlet, is the counterweighted Eagan Sturdy Seal, for which, although extensively advertised, no clear diagram, picture or photograph is available. The lid is lowered horizontally by a scissors frame arrangement, the counterweight urges the lid closed, while the cable, cord, string, wire, or the like moves the counterweight allowing the lid to open. This has the advantage over other systems that the counterweight is used to hold the lid closed, while the cable, cord, string, wire or the like, opens the lid, when pulled by a machine. In most inlets the machine pulls the lid closed, as the strings stretch, unless the inlet strings are perfectly adjusted, individual inlets may stay open.

DESCRIPTION OF THE INVENTION

The invention in one broad embodiment is directed to an air inlet for ventilation comprising an upper aperture and a lower aperture joined by a tubular passage defined by surrounding side walls extending between said apertures. The upper aperture has a generally planar edge and is adapted to allow airflow from a corresponding aperture in a substrate. The lower aperture has a planar edge generally parallel to the edge of the upper aperture and is locatable below said substrate. The lower aperture has a lid movable between a closed position blocking the passage, and at least one open position allowing air flow through the passage. The tubular passage is generally rectangular in cross section. It has side walls forming two pairs of opposed parallel walls connected at their side edges. There are spaced apart parallel first and second axles extending between one pair of opposed parallel side walls, each axle has two yokes mounted thereon adjacent the side walls. The yokes have a central disk and first and second arms extending outward from said disk at an acute angle. There is an upper metal pull bar substantially parallel to a plane formed by the axles, and the pull bar is joined to the yokes by first clevis pinds journalled in the pull bar and the first arms of the yokes. Two lower plastic connecting bars are aligned substantially perpendicular to the axles. The connecting bars are joined to the yokes by second clevis pins journalled in the connecting bars and said second arms of said yokes. The yokes and clevis pins hold the pull bar and connecting bars in firm relationship with each other. The lower plastic connecting bars are attached to the lid. Although the two connecting bars are independent of each other, one or more connecting cross struts could be used to join them together. The pull bar has a default position wherein the lid is in closed position. The yokes are rotatable from the default position where the arms are generally upward and the clevis pins aligned parallel to the edges of the upper and lower apertures. When the pull bar is displaced from its default position away from the first axle toward the second axle the yokes are angularly rotated away from the default position so the first arms are closer to the edge of the upper aperture and the second arms are closer to the edge of the lower aperture, whereby the lower plastic connecting bars are displaced away from the edge of the upper aperture, and the lid is displaced away from the edge of the lower aperture into an open position, the angle of rotation of the yokes determining the displacement of the lid. Preferably the axles have square end sleeves, which matingly engage square apertures in the yokes in the centre of the disks. Preferably the first axle has a square cross section. This keeps the yokes on the first axle in fixed relation to the first axle and hence the pull bar and the yokes on the second axle move together with the first axle. The connecting bars move with their associated clevis pins together with the first axle. Preferably the upper aperture's generally planar edge has a surrounding planar lip extending generally perpendicular to said side walls. The lip is adapted to fit against a substrate. Generally holes are drilled through the lip at installation and it is secured to the substrate by screws or bolts, staples, or adhesive may also be used. Preferably the upper metal pull bar has side rails substantially perpendicular to the axles, and cross rails joining the side rails parallel to the axles. Preferably the side rails are joined to the yokes by first clevis pins journalled in the side rails and the first arms of the yokes. Preferably the lower plastic connecting bars extend downward to the lid and are attached thereto. Preferably the connecting bars have end projections extending the same distance downward. The projections have downward tabs at their bottom. These downward tabs have therein apertures, which are substantially at right angles to the connecting bars. Preferably the lid has four apertures to register with the tabs of the connecting bars. When registered the tabs pass through the lid. Preferably there are paired lid locking bars on the lower surface of the lid parallel to the axles engaging the apertures of the tabs of the connecting bars at both ends, and holding the lid in fixed relation to the connecting bars. The lid locking bars are flexible and can be removed together with the lid. Typically this is done at installation so that holes can be drilled through the lip to attach the inlet to the substrate, or to check and repair the interior of the installed inlet. Preferably each lid locking bar has a central tab to engage a recess in the lower surface of the lid, which also hold the lid locking bar in position preventing it sliding out. Preferably each lid locking bar has central wings extending perpendicular to the lid locking bar on either side. These wings are present to prevent the lid locking bars when removed to take off the lid from dropping between floor slats in a hog barn. When this occurs the lid locking bar has to be extracted from under the floor. The wings prevent this occurrence. Preferably the side walls comprise paired opposed cross walls parallel to said axles. Preferably at least one spring is attached to a first cross wall adjacent said first axle, and to a first cross rail of the pull bar adjacent the first axle. The spring urges the pull bar into the default position. Typically two springs are used. Preferably a cord a cord passes through an aperture in a second cross wall adjacent the second axle and is attached to a second cross rail of the pull bar adjacent the second axle, whereby the cord can displace the pull bar from its default position toward an open position. The cord may be attached by other cords to a machine so an array of inlets my be opened together. The term cord as used herein is meant to cover cords, wires, cables, strings, and the like, as understood by those skilled in the art.

The invention in a second broad embodiment is directed to an improved air inlet for ventilation comprising an upper aperture and a lower aperture joined by a tubular passage defined by surrounding side walls extending between said apertures. The upper aperture has a generally planar edge and is adapted to allow airflow from a corresponding aperture in a substrate. The lower aperture has a planar edge generally parallel to the edge of the upper aperture and is locatable below said substrate. The lower aperture has a lid movable between a closed position blocking the passage, and at least one open position allowing air flow through the passage. The tubular passage is generally rectangular in cross section. It has side walls forming two pairs of opposed parallel walls connected at their side edges. The improvement comprises spaced apart parallel first and second axles extending between one pair of opposed parallel side walls, each axle has two yokes mounted thereon adjacent the side walls. The yokes have a central disk and first and second arms extending outward from said disk at an acute angle. There is an upper metal pull bar substantially parallel to a plane formed by the axles, and the pull bar is joined to the yokes by first clevis pins journalled in the pull bar and the first arms of the yokes. Two lower plastic connecting bars are aligned substantially perpendicular to the axles. The connecting bars are joined to the yokes by second clevis pins journalled in the connecting bars and said second arms of said yokes. The yokes and clevis pins hold the pull bar and connecting bars in firm relationship with each other. The lower plastic connecting bars are attached to the lid. Although the two connecting bars are independent of each other, one or more connecting cross struts could be used to join them together. The pull bar has a default position wherein the lid is in closed position. The yokes are rotatable from the default position where the arms are generally upward and the clevis pins aligned parallel to the edges of the upper and lower apertures. When the pull bar is displaced from its default position away from the first axle toward the second axle the yokes are angularly rotated away from the default position so the first arms are closer to the edge of the upper aperture and the second arms are closer to the edge of the lower aperture, whereby the lower plastic connecting bars are displaced away from the edge of the upper aperture, and the lid is displaced away from the edge of the lower aperture into an open position, the angle of rotation of the yokes determining the displacement of the lid. Preferably the axles have square end sleeves, which matingly engage square apertures in yokes in the centre of the disks. Preferably the first axle has a square cross section. This keeps the yokes on the first axle in fixed relation to the first axle and hence the pull bar and the yokes on the second axle move together with the first axle. The connecting bars move with their associated clevis pins together with the first axle. Preferably the upper aperture's generally planar edge has a surrounding planar lip extending generally perpendicular to said side walls. The lip is adapted to fit against a substrate. Generally holes are drilled through the lip at installation and it is secured to the substrate by screws or bolts, staples or adhesive may also be used. Preferably the upper metal pull bar has side rails substantially perpendicular to the axles, and cross rails joining the side rails parallel to the axles. Preferably the side rails are joined to the yokes by first clevis pins journalled in the side rails and the first arms of the yokes. Preferably the lower plastic connecting bars extend downward to the lid and are attached thereto. Preferably the connecting bars have end projections extending the same distance downward. The projections have downward tabs at their bottom. These downward tabs have therein apertures, which are substantially at right angles to the connecting bars. Preferably the lid has four apertures to register with the tabs of the connecting bars. When registered the tabs pass through the lid. Preferably there are paired lid locking bars on the lower surface of the lid parallel to the axles engaging the apertures of the tabs of the connecting bars at both ends, and holding the lid in fixed relation to the connecting bars. The lid locking bars are flexible and can be removed together with the lid. Typically this is done at installation so that holes can be drilled through the lip to attach the inlet to the substrate, or to check and repair the interior of the installed inlet. Preferably each lid locking bar has a central tab to engage a recess in the lower surface of the lid, which also hold the lid locking bar in position preventing it sliding out. Preferably each lid locking bar has central wings extending perpendicular to the lid locking bar on either side. These wings are present to prevent the lid locking bars when removed to take off the lid from dropping between floor slats in a hog barn. When this occurs the lid locking bar has to be extracted from under the floor. The wings prevent this occurrence. Preferably the side walls comprise paired opposed cross walls parallel to said axles. Preferably at least one spring is attached to a first cross wall adjacent said first axle, and to a first cross rail of the pull bar adjacent the first axle. The spring urges the pull bar into the default position. Typically two springs are used. Preferably a cord a cord passes through an aperture in a second cross wall adjacent the second axle and is attached to a second cross rail of the pull bar adjacent the second axle, whereby the cord can displace the pull bar from its default position toward an open position. The cord may be attached by other cords to a machine so an array of inlets my be opened together. The term cord as used herein is meant to cover cords, wires, cables, strings, and the like, as understood by those skilled in the art.

The invention in a third broad embodiment is directed to an attic air inlet for ventilation comprising an upper aperture and a lower aperture joined by a tubular passage defined by surrounding side walls extending between said apertures. The upper aperture has a generally planar edge and is adapted to allow airflow from a corresponding aperture in a substrate. The lower aperture has a planar edge generally parallel to the edge of the upper aperture and is locatable below said substrate. The lower aperture has a lid movable between a closed position blocking the passage, and at least one open position allowing air flow through the passage. The tubular passage is generally rectangular in cross section. It has side walls forming two pairs of opposed parallel walls connected at their side edges. There are spaced apart parallel first and second axles extending between one pair of opposed parallel side walls, each axle has two yokes mounted thereon adjacent the side walls. The yokes have a central disk and first and second arms extending outward from said disk at an acute angle. There is an upper metal pull bar substantially parallel to a plane formed by the axles, and the pull bar is joined to the yokes by first clevis pins journalled in the pull bar and the first arms of the yokes. Two lower plastic connecting bars are aligned substantially perpendicular to the axles. The connecting bars are joined to the yokes by second clevis pins journalled in the connecting bars and said second arms of said yokes. The yokes and clevis pins hold the pull bar and connecting bars in firm relationship with each other. The lower plastic connecting bars are attached to the lid. Although the two connecting bars are independent of each other, one or more connecting cross struts could be used to join them together. The pull bar has a default position wherein the lid is in closed position. The yokes are rotatable from the default position where the arms are generally upward and the clevis pins aligned parallel to the edges of the upper and lower apertures. When the pull bar is displaced from its default position away from the first axle toward the second axle the yokes are angularly rotated away from the default position so the first arms are closer to the edge of the upper aperture and the second arms are closer to the edge of the lower aperture, whereby the lower plastic connecting bars are displaced away from the edge of the upper aperture, and the lid is displaced away from the edge of the lower aperture into an open position, the angle of rotation of the yokes determining the displacement of the lid. Preferably the axles have square end sleeves, which matingly engage square apertures in yokes in the centre of the disks. Preferably the first axle has a square cross section. This keeps the yokes on the first axle in fixed relation to the first axle and hence the pull bar and the yokes on the second axle move together with the first axle. The connecting bars move with their associated clevis pins together with the first axle. Preferably the upper aperture's generally planar edge has a surrounding planar lip extending generally perpendicular to said side walls. The lip is adapted to fit against a substrate. Generally holes are drilled through the lip at installation and it is secured to the substrate by screws or bolts. Preferably the upper metal pull bar has side rails substantially perpendicular to the axles, and cross rails joining the side rails parallel to the axles. Preferably the side rails are joined to the yokes by first clevis pins journalled in the side rails and the first arms of the yokes. Preferably the lower plastic connecting bars extend downward to the lid and are attached thereto. Preferably the connecting bars have end projections extending the same distance downward. The projections have downward tabs at their bottom. These downward tabs have therein apertures, which are substantially at right angles to the connecting bars. Preferably the lid has four apertures to register with the tabs of the connecting bars. When registered the tabs pass through the lid. Preferably there are paired lid locking bars on the lower surface of the lid parallel to the axles engaging the apertures of the tabs of the connecting bars at both ends, and holding the lid in fixed relation to the connecting bars. The lid locking bars are flexible and can be removed together with the lid. Typically this is done at installation so that holes can be drilled through the lip to attach the inlet to the substrate, or to check and repair the interior of the installed inlet. Preferably each lid locking bar has a central tab to engage a recess in the lower surface of the lid, which also hold the lid locking bar in position preventing it sliding out. Preferably each lid locking bar has central wings extending perpendicular to the lid locking bar on either side. These wings are present to prevent the lid locking bars when removed to take off the lid from dropping between floor slats in a hog barn. When this occurs the lid locking bar has to be to extracted from under the floor. The wings prevent this occurrence. Preferably the side walls comprise paired opposed cross walls parallel to said axles. Preferably at least one spring is attached to a first cross wall adjacent said first axle, and to a first cross rail of the pull bar adjacent the first axle. The spring urges the pull bar into the default position. Typically two springs are used. Preferably a cord passes through an aperture in a second cross wall adjacent the second axle and is attached to a second cross rail of the pull bar adjacent the second axle, whereby the cord can displace the pull bar from its default position toward an open position. The cord may be attached by other cords typically a cable or cables to a machine so an array of inlets my be opened together. The term cord as used herein is meant to cover cords, wires, cables, strings, and the like, as understood by those skilled in the art.

The difference over the prior art is that the four points of contact between the connecting bars and the lid stay in a plane when moved by the pull bar and axles. The lid is displaced the same distance in the same direction at each point, and is always parallel to the plane of the bottom of the tube. Another difference is that the lid is easily and quickly removable and replaceable without tools, no screws, bolts, nuts or other fasteners are involved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a top plan view of the invention in closed position.

FIG. 2 shows a side cross sectional elevational view of the embodiment of FIG. 1 in closed position.

FIG. 3 shows a side cross sectional elevational view of the embodiment of FIG. 1 in open position.

FIG. 4 shows a bottom plan view of the embodiment of FIG. 1.

FIG. 5 shows a side elevational view of the embodiment of FIG. 1.

FIG. 6 shows a side elevational view of a lid locking bar of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention is now illustrated by reference to preferred embodiments thereof. Air inlet 10 has rectangular box frame 12 with upright walls 14, 16, 18, and 20, and top mounting lip 22. Box frame 12 is typically hard polyurethane foam 23 inch square and ½ inch thick, with lip 22 extending 2½ inch outward, it is 4½ inch deep. Bottom ventilating lid 24 abuts box frame 12 in closed position, bottom lid 24 is typically foamed plastic, 27 inch square and ⅝ inch thick. Metal rods 26 and 28, extend between walls 16 and 20 in which they are journalled. U yokes 30 and 32, of nylon, are rotatably mounted on square metal rod 26, typically aluminum, inch square, which has square socket in square base 128 engaging square apertures 130 in yokes 30 and 32. U yokes 34 and 36, also nylon, are similarly rotatably mounted on round metal rod 28, typically stainless steel, ¼ inch diameter, which has round socket in square base 132 engaging square aperture 134 in yokes 34 and 36. The ends of rods 26 and 28 are rotatably received in inside bushings (not shown) in walls 16 and 20. Upper metal pull bar 40, typically 16 gauge, has side rails 42, 44 and central rail 46, connected by transverse rails 48 and 50. Pull bar 40 is attached to arms 52, 54, 56, and 58 of U yokes 30, 32, 34, 36, by clevis pins 60, 62, 64, and 66, which all have push nuts. Lower plastic connecting bar 68, nylon, ¼ inch thick, is attached to arms 70 and 76 of U yokes 30 and 36 by clevis pins 78 and 80, while plastic connecting bar 82, nylon, also ¼ inch thick, is likewise attached to arms 72 and 74 of U yokes 32 and 34 by clevis pins 84 and 86. clevis pins 78, 80, 84, 86 all have push nuts. Lower plastic connecting bars 68 and 82 are attached to bottom lid 24. Springs 88 and 90, typically stainless steel, are attached to wall 14 by eyebolts 92 and 94, secured by nuts and washers and transverse rail 50 of pull bar 40 by S hooks 96 and 98, urge pull bar 40 toward wall 14. Cord 100, typically nylon, attached to transverse bar 48 of pull bar 40 by S hook 102 passes through wall 18, through string bushing 126 ending at loop 104, which can be used to displace pull bar 40 toward wall 18. Loop 104 is typically attached to a machine controlled cable, cord, string, wire or the like.

Square metal rod 26 engages square apertures 130 in U yokes 30 and 32 through square bases 128. Round metal rod 28 similarly engages square apertures 134 in U yokes 34 and 36 through square bases 134. Movement of pull bar 40 thus rotates U yoke 32 by arm 54 and U yoke 30 by arm 52 the same angle as it rotates U yoke 34 by arm 56 and U yoke 36 by arm 58. Pull bar and U yokes move the same angle. This ensures that arms 70 and 76 attached to connecting bar 68 and arms 72 and 74 attached to connecting bar 82 have the same angular displacement, thus connecting bars 68 and 82 are displaced the same perpendicular distance. Lid 24 is thus lowered or raised the same amount at attachment points. In default position the distance between transverse rail 48 and wall 18 is about 8 inches and lid 24 is closed. When the distance between transverse rail 48 and wall 18 is reduced to about 6¼ inches, lid 24 is lowered about 1½ inches and is about half open. When the distance between transverse rail 48 and wall 18 is reduced to about 5 inches, lid 24 is lowered about 3¾ inches and is about full open. As appreciated by those skilled in the art this confers significant control over the degree of lid opening.

Metal side rail 44 has downward end flanges 106 and 108 to receive clevis pins 62 and 64. Plastic connecting bar 82 has downward projections 108 and 110, which have projecting tabs 112 and 114 which pass through apertures 120 of bottom lid 24. Tabs 112 and 114 have apertures 124 and 126 which are which are engaged by transverse lid locking bars 116 and 118, which are ¼ inch thick plastic. Tabs 112 and 114 fit snugly into apertures 120 to minimize play. Similarly lid locking bars 116 and 118 fit snugly into apertures 124 and 126 to minimize play. Box frame 12 has attached surrounding plastic bottom flanges 120, fixed to lid 24 by strips 122, which provides an air seal when lid 24 is in contact with box frame 12. FIG. 2 shows the invention in closed (default) position. FIG. 3 shows the invention in open (deployed) position.

Lid 24 is designed for quick attachment, detachment and reattachment. It is made of soft polystyrene insulation foam. Lid locking bars 116 and 118 have optional wings 136 extending at their midpoints some 1½ inches on either side, and tab 140, which engages recess 138 in lid 24. Optional wings 136 when present prevent a dropped lid locking bar falling between floor slats, which are generally present in hog another barn floors. Tab 140 snugly engages recess 138 thus preventing lid locking bar 116 or 118 moving out of position. Lid locking bars 116 and 118 are nylon and can be easily removed to take off lid 24, for maintenance, for instance. Lid 24 is also removed to allow screws to be driven through mounting lip 22 into the barn ceiling, securing air inlet 10 to it. Lid 24 is then replaced by pushing it up so tabs 112 and 114 engage slots 120, then the ends of lid locking bars 116 and 118 are pushed through apertures 124 and 126 in tabs 112 and 114, tabs 140 snap into recesses 138 to hold the lid locking bars in place.

As those skilled in the art would realize these preferred described details and materials and components can be subjected to substantial variation, modification, change, alteration, and substitution without affecting or modifying the function of the described embodiments.

Although embodiments of the invention have been described above, it is not limited thereto, and it will be apparent to persons skilled in the art that numerous modifications and variations form part of the present invention insofar as they do not depart from the spirit, nature and scope of the claimed and described invention. 

1. Air inlet for ventilation comprising an upper aperture and a lower aperture joined by a tubular passage defined by surrounding side walls extending between said apertures, said upper aperture having a generally planar edge and said upper aperture being adapted to allow airflow from a corresponding aperture in a substrate, said lower aperture having a planar edge generally parallel to the edge of said upper aperture and locatable below said substrate, said lower aperture having a lid movable between a closed position blocking said passage, and at least one open position allowing air flow through said passage, said tubular passage being generally rectangular in cross section, said side walls forming two pairs of opposed parallel walls connected at their side edges, spaced apart parallel first and second axles extending between one pair of opposed parallel side walls, each axle having two yokes mounted thereon adjacent said side walls, said yokes having a central disk and first and second arms extending outward from said disk at an acute angle, an upper metal pull bar substantially parallel to a plane formed by said axles, and said pull bar being joined to said yokes by first clevis pins journalled in said pull bar and said first arms of said yokes, two lower plastic connecting bars aligned substantially perpendicular to said axles, said connecting bars being joined to said yokes by second clevis pins journalled in said connecting bars and said second arms of said yokes, said lower plastic connecting bars being attached to said lid, said pull bar having a default position wherein said lid is in closed position, said yokes being rotatable from said default position where said arms are generally upward and said clevis pins aligned parallel to said edges of said upper and lower apertures, when said pull bar is displaced from said default position away from said first axle toward said second axle said yokes are angularly rotated away from said default position so said first arms are closer to said edge of said upper aperture and said second arms are closer to the edge of said lower aperture, whereby said lower plastic connecting bars are displaced away from said edge of said upper aperture, and said lid is displaced away from said edge of said lower aperture into an open position, the angle of rotation of said yokes determining the displacement of said lid.
 2. Inlet of claim 1, wherein said axles have square end sleeves, which matingly engage square apertures in said yokes.
 3. Inlet of claim 2, wherein said first axle has a square cross section.
 4. Inlet of claim 1, wherein said upper aperture has a generally planar edge and a surrounding planar lip extending generally perpendicular to said side walls, said lip being adapted to fit against a substrate, said upper metal pull bar having side rails substantially perpendicular to said axles, and cross rails joining said side rails parallel to said axles, said side rails being joined to said yokes by first clevis pins journalled in said side rails and said first arms of said yokes, said lower plastic connecting bars extending downward to said lid and being attached thereto.
 5. Air inlet of claim 4, wherein said connecting bars have end projections extending the same distance downward, said projections having downward tabs at their bottom, said downward tabs having therein apertures, said apertures being substantially at right angles to said connecting bars said lid having four apertures to register with said tabs of said connecting bars, said tabs when registered passing through said lid paired lid locking bars on the lower surface of said lid parallel to said axles engaging said apertures of said tabs of said connecting bars at both ends, and holding said lid in fixed relation to said connecting bars.
 6. Air inlet of claim 5, wherein each said lid locking bar has a central tab to engage a recess in said lower surface of said lid.
 7. Air inlet of claim 6, wherein each said lid locking bar has central wings extending perpendicular to said lid locking bar on either side.
 8. Air inlet of claim 1 wherein said side walls comprise paired opposed cross walls parallel to said axles.
 9. Air inlet of claim 8 wherein at least one spring is attached to a first cross wall adjacent said first axle, and to a first cross rail of said pull bar adjacent said first axle, said spring urging said pull bar into said default position.
 10. Air inlet of claim 9 wherein a cord passes through an aperture in a second cross wall adjacent said second axle and is attached to a second cross rail of said pull bar adjacent said second axle, whereby said cord can displace said pull bar from said default position toward an open position.
 11. Air inlet for ventilation comprising an upper aperture and a lower aperture joined by a tubular passage defined by surrounding side walls extending between said apertures, said upper aperture having a generally planar edge and said upper aperture being adapted to allow airflow from a corresponding aperture in a substrate, said lower aperture having a planar edge generally parallel to the edge of said upper aperture and locatable below said substrate, said lower aperture having a lid movable between a closed position blocking said passage, and at least one open position allowing air flow through said passage, said tubular passage being generally rectangular in cross section, said side walls forming two pairs of opposed parallel walls connected at their side edges, the improvement comprising spaced apart parallel first and second axles extending between one pair of opposed parallel side walls, each axle having two yokes mounted thereon adjacent said side walls, said yokes having a central disk and first and second arms extending outward from said disk at an acute angle, an upper metal pull bar substantially parallel to a plane formed by said axles, and said pull bar being joined to said yokes by first clevis pins journalled in said pull bar and said first arms of said yokes, two lower plastic connecting bars aligned substantially perpendicular to said axles, said connecting bars being joined to said yokes by second clevis pins journalled in said connecting bars and said second arms of said yokes, said lower plastic connecting bars being attached to said lid, said pull bar having a default position wherein said lid is in closed position, said yokes being rotatable from said default position where said arms are generally upward and said clevis pins aligned parallel to said edges of said upper and lower apertures, when said pull bar is displaced from said default position away from said first axle toward said second axle said yokes are angularly rotated away from said default position so said first arms closer to said edge of said upper aperture and said second arms closer to the edge of said lower aperture, whereby said lower plastic connecting bars are displaced away from said edge of said upper aperture, and said lid is displaced away from said edge of said lower aperture into an open position, the angle of rotation of said yokes determining the displacement of said lid.
 12. Inlet of claim 11, wherein said axles have square end sleeves, which matingly engage square apertures in said yokes.
 13. Inlet of claim 12, wherein said first axle has a square cross section.
 14. Inlet of claim 11, wherein said upper aperture has a generally planar edge and a surrounding planar lip extending generally perpendicular to said side walls, said lip being adapted to fit against a substrate, said upper metal pull bar having side rails substantially perpendicular to said axles, and cross rails joining said side rails parallel to said axles, said side rails being joined to said yokes by first clevis pins journalled in said side rails and said first arms of said yokes, said lower plastic connecting bars extending downward to said lid and being attached thereto.
 15. Air inlet of claim 14, wherein said connecting bars have end projections extending the same distance downward, said projections having downward tabs at their bottom, said downward tabs having therein apertures, said apertures being substantially at right angles to said connecting bars said lid having four apertures to register with said tabs of said connecting bars, said tabs when registered passing through said lid paired lid locking bars on the lower surface of said lid parallel to said axles engaging said apertures of said tabs of said connecting bars at both ends, and holding said lid in fixed relation to said connecting bars.
 16. Air inlet of claim 15, wherein each said lid locking bar has a central tab to engage a recess in said lower surface of said lid.
 17. Air inlet of claim 16, wherein each said lid locking bar has central wings extending perpendicular to said lid locking bar on either side.
 18. Air inlet of claim 11 wherein said side walls comprise paired opposed cross walls parallel to said axles, and in at least one spring is attached to a first cross wall adjacent said first axle, and to a first cross rail of said pull bar adjacent said first axle, said spring urging said pull bar into said default position, and a cord passes through an aperture in a second cross wall adjacent said second axle and is attached to a second cross rail of said pull bar adjacent said second axle, whereby said cord can displace said pull bar from said default position toward an open position.
 19. Attic air inlet for ventilation comprising an upper aperture and a lower aperture joined by a tubular passage defined by surrounding side walls extending between said apertures, said upper aperture having a generally planar edge and a surrounding planar lip extending generally perpendicular to said side walls, said lip being adapted to fit against a substrate, and said upper aperture being adapted to allow airflow from a corresponding aperture in a substrate, said lower aperture having a planar edge generally parallel to the edge of said upper aperture and locatable below said substrate, said lower aperture having a lid movable between a closed position blocking said passage, and at least one open position allowing air flow through said passage, said tubular passage being generally rectangular in cross section, said side walls forming two pairs of opposed parallel walls connected at their side edges, spaced apart parallel first and second axles extending between one pair of opposed parallel side walls, each axle having two yokes mounted thereon adjacent said side walls, said yokes having a central disk and first and second arms extending outward from said disk at an acute angle, an upper metal pull bar substantially parallel to a plane formed by said axles, and said pull bar having side rails substantially perpendicular to said axles, and cross rails joining said side rails parallel to said axles, said side rails being joined to said yokes by first clevis pins journalled in said side rails and said first arms of said yokes, said axles having square end sleeves, which matingly engage square apertures in said yokes, said first axle having a square cross section, two lower plastic connecting bars aligned substantially perpendicular to said axles, said connecting bars being joined to said yokes by second clevis pins journalled in said connecting bars and said second arms of said yokes, said lower plastic connecting bars connecting bars extending downward to said lid and being attached thereto, said pull bar having a default position wherein said lid is in closed position, said yokes being rotatable from said default position where said arms are generally upward and said clevis pins aligned parallel to said edges of said upper and lower apertures, when said pull bar is displaced from said default position away from said first axle toward said second axle said yokes are angularly rotated away from said default position so said, first arms closer to said edge of said upper aperture and said second arms closer to the edge of said lower aperture, whereby said lower plastic connecting bars are displaced away from said edge of said upper aperture, and said lid is displaced away from said edge of said lower aperture into an open position, the angle of rotation of said yokes determining the displacement of said lid.
 20. Attic air inlet of claim 19, wherein said connecting bars have end projections extending the same distance downward, said projections having downward tabs at their bottom, said downward tabs having therein apertures, said apertures being substantially at right angles to said connecting bars said lid having four apertures to register with said tabs of said connecting bars, said tabs when registered passing through said lid paired lid locking bars on the lower surface of said lid parallel to said axles engaging said apertures of said tabs of said connecting bars at both ends, and holding said lid in fixed relation to said connecting bars, and each said lid locking bar has a central tab to engage a recess in said lower surface of said lid and each said lid locking bar has central wings extending perpendicular to said lid locking bar on either side and said side walls comprise paired opposed cross walls parallel to said axles and at least one spring is attached to a first cross wall adjacent said first axle, and to a first cross rail of said pull bar adjacent said first axle, said spring urging said pull bar into said default position and a cord passes through an aperture in a second cross wall adjacent said second axle and is attached to a second cross rail of said pull bar adjacent said second axle, whereby said cord can displace said pull bar from said default position toward an open position. 